The child dropped 12 to 14 feet from a window of a home in the first block of 38th Avenue about 11:30 a.m., said San Mateo police Sgt. Dave Norris. The first officer to arrive, about 90 seconds later, found the boy conscious and breathing.

An ambulance took the boy, whose family was not identified, to a hospital for treatment. The extent of his injuries was not known.

Norris said family members were home at the time, and while there are no signs indicating foul play, the investigation is ongoing.

There was some kind of activity outside the house, and the boy may have gone over to the window to see what was happening, though police aren't sure exactly what led to the child's fall. A screen was in place on the window, police said.